DESCRIPTION: Cryptosporidium parvum is an AIDS-OI pathogen and Category B agent. It is a significant water- and food-borne protozoan parasite that can cause severe watery diarrhea in humans and animals. Currently, only a single drug (i.e., nitazoxanide [NTZ]) is approved for treating cryptosporidiosis in immunocompetent (but not immunocompromized) patients in the United States. However, NTZ is not 100% effective against cryptosporidiosis. Potential drug resistance may also be developed in Cryptosporidium, similar to the drug resistance problem in malarial parasites and coccidia. Therefore, there is an urgent need to develop new anti-Cryptosporidium drugs. Our long-term goal of this translational research is to characterize the molecular and biochemical features of the essential enzymes in the C. parvum glycolytic pathway as potential drug targets. Because C. parvum relies solely on glycolysis for its energy, we hypothesize that the bacterial-type CpHK responsible for the entry step of reaction in the glycolytic pathways could serve as rational drug targets in this parasite. To test the hypothesis, we will perform experiments to characterize the biochemical features of CpHK and identify CpHK inhibitors for future drug development via HTS of compound libraries, characterize the inhibitory kinetics of top hits, and test their efficacies against C. parvum growth in vitro. The major goal of this exploratory/developmental R21 project is to identify hits that inhibit both CpHK enzyme activity and the parasite growth in vitro, which would produce conclusive data for further studying the mechanism of inhibition, structure-activity relationship, and to synthesize new analogs of hits for lead optimization, as well as to assess the efficacies of hits and leads agains cryptosporidial infection in animal models.